Pin commit hash in model connectors (#455)

[hholb]

resolves #455

Related: #454

Overview

Both HFConnector and GitHubConnector now attempt to retrieve a commit hash from their remote repos and store it in their ModelMetadata.model_version when instantiated. If no commmit hash is found, a ConnectorInvalidRevisionError is raised.

The pinned commit hash is then used when stage() is called to pull down the same model each time the entrypoint is run.

Discussion

In GitHubConnector I am using the github api to get the commit info. This only works with public repos.

Testing

New unit tests in tests/test_models.py confirm the commit hash is correctly stored and used within stage().

Documentation

No documentation updated.

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📚 Documentation preview 📚: https://garden-ai--464.org.readthedocs.build/en/464/

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.70588% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 75.94%. Comparing base (cd758d8) to head (45ebff4).

Files	Patch %	Lines
garden_ai/model_connectors/github_conn.py	80.95%	4 Missing :warning:
garden_ai/model_connectors/hugging_face.py	83.33%	2 Missing :warning:
garden_ai/model_connectors/exceptions.py	66.66%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #464 +/- ## ========================================== + Coverage 75.42% 75.94% +0.52% ========================================== Files 50 51 +1 Lines 3198 3264 +66 ========================================== + Hits 2412 2479 +67 + Misses 786 785 -1 ```

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